A systematic review and meta-analysis of suicidality in autistic and possibly autistic people without co-occurring intellectual disability.

Background: Suicidality is highly prevalent in autistic people without co-occurring intellectual disabilities, and high autistic traits are found in adults who have attempted suicide. However, prevalence rates for both autistic and possibly autistic people have not been synthesised meta-analytically.

Aims: To (1) calculate pooled prevalence estimates of suicidality in autistic people and possibly autistic people without co-occurring intellectual disability; (2) evaluate the influence of participant and study level characteristics on heterogeneity; and (3) determine the quality of evidence.

Methods: Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines were followed. PsycINFO, Embase, MEDLINE and Web of Science were systematically searched from 1992 to January 25, 2022. Empirical quantitative studies reporting prevalence of suicidal ideation, suicide plans, or suicide attempts and behaviours were considered for inclusion. Random effects models were used to estimate pooled prevalence of each suicidality outcome with 95% confidence intervals. Heterogeneity was explored using sensitivity and moderator analyses.

Results: Data from 48,186 autistic and possibly autistic participants in 36 primary studies were meta-analysed. Pooled prevalence of suicidal ideation was 34.2% (95% CI 27.9-40.5), suicide plans 21.9% (13.4-30.4), and suicidal attempts and behaviours 24.3% (18.9-29.6). High levels of heterogeneity (I² > 75) were observed in all three analyses. Estimates did not differ between autistic or possibly autistic samples. Geographical location (p = 0.005), transgender or gender non-conforming samples (p < 0.001) and type of report (p < 0.001) significantly moderated suicidal ideation, whereas age group (p = 0.001) and measure of suicidality (p = 0.001) significantly moderated suicide plans. There was a significant association between the proportion of male participants and prevalence of suicide plans, with a decrease in the proportion of males for every unit change of suicide plan prevalence (p = 0.013). No variables were found to moderate estimates of suicide attempts and behaviours.

Conclusions: The results confirm suicidality is highly prevalent in both autistic and possibly autistic people without co-occurring intellectual disability and highlights potential moderators. Possibly autistic individuals require more attention in clinical and research considerations going forward to further understand and prevent suicide in both groups.